In recent years, means for simply acquiring 3-dimensional shapes has been requested along with lower priced 3D printers.
As means for acquiring the 3-dimensional shapes of subjects, there are active and passive schemes. The active schemes are, for example, schemes of irradiating subjects with light and acquiring 3-dimensional shapes based on reflected light from the subjects and are not simple schemes in terms of power consumption, component cost, or the like. In contrast to the active schemes, the passive schemes are schemes of acquiring 3-dimensional shapes without irradiating subjects with light and are simpler schemes than the active schemes. As the passive methods, for example, a scheme of generating a depth map by requesting correspondence between images using stereo cameras and a scheme of acquiring polarized mages in a plurality of directions and generating a normal-line map are used.
In the scheme using a stereo camera in the passive schemes, a problem that the depth of a flat portion of a subject may not be acquired is known. In the scheme using a polarized image in a plurality of directions, the fact that the relative surface shape of a subject can be acquired, but an absolute distance may not be acquired is known. Further, in the scheme using a polarized image in a plurality of directions, the fact that there is the uncertainty of 180 degrees at an azimuth angle of the normal line of a subject is known. Accordingly, in Patent Literature 1, by disposing polarization filters having different polarization directions in pixels of an image sensor mounted on an individual camera of a stereo camera, acquisition of a depth map by the stereo camera and acquisition of a normal-line map by polarization imaging are simultaneously performed. Further, in Patent Literature 1, the uncertainty of 180 degrees in the normal-line map can be solved and an absolute distance can be acquired by referring to a depth map.